Method and device for metering powders and pasty products

Abstract

The invention relates to a device for metering powders, comprising: a block (1) inside which a dose (2) of the desired quantity is formed, a device (3) for ejecting the dose (2), a bore (4) having a diameter corresponding to the quantity of the dose to be created, for forming the dose, the bore (4) being connected at its inlet to a chamber (5) of conical and cylindrical shape containing a free piston (6), the bore (4) being connected at its outlet to a chamber (10) identical to the chamber (5), a programmable logic controller controlling the metering device, the device (3) for ejecting the dose comprising a dose ejector (20) having a slightly smaller diameter than the bore (4), and a free piston (21), the dose ejector (20) being moved by the free piston (21).

Description

[0001] TITLE OF THE INVENTION:

[0002] METHOD AND DEVICE FOR DOSING POWDERS AND PASTY PRODUCTS

[0003] The present invention is intended for the dosing of very small quantities of powdery or pasty products.

[0004] More particularly dosing powders, with difficult flow to reach quantities equal to or even less than 1 mg.

[0005] A powder with a difficult flow and often a tendency to settle can be likened to a paste, which leads to the design of a process enabling the dosing of tiny quantities of paste in order to resolve or even meet unmet needs for powders.

[0006] Fig. 1

[0007] The basic principle is illustrated in Fig. 1 which represents an example of implementation.

[0008] The assembly comprises a block (1) inside which a dose (2) of the desired size is formed, for example 1 mg.

[0009] This dose is ejected by means of the device (3), represented by figures (F2), (F3) and (F4)

[0010] The dose is formed in a bore (4) of a diameter corresponding to the size of the dose to be created. For example, 1 mm in diameter. The bore (4) is connected at its inlet to a chamber (5) of conical and cylindrical shape containing a free piston (6). The chamber (5) is connected to the storage tank (7) of the product to be dosed. It has a free piston (8) for products without free flow. A fully opening valve (9) connects the chamber (5) to the tank (7).

[0011] The bore (4) at its outlet is connected to a chamber (10) identical to the chamber (5) each also comprising a free piston (11)

[0012] The set of pistons is moved by means of a vacuum source (12) and pressure source (13), each having a valve or distributor, such as (14) all controlled by a programmable controller

[0013] The ejection device (3) represented below by (Fig2, 3,4) operates according to the following process:

[0014] Fig. 2 represents the free space left by the product to be dosed (2) after its ejection represented by Fig. 3). It also shows by position (3a), the possibility of injecting a jet of air allowing the dose to be cut at its exit. Possibility required for very viscous pastes.

[0015] (Fig.3) shows the dose ejection position. In position (23), a threaded rod is shown, allowing the desired dose size to be fixed by the nut (3a). Figure (4) shows the closing position by the ball (15), fixed on the rod moved by the free piston (17). The drillings require significant precision that can be achieved, for example, by 3D printing, shown in Fig.5, with intervals (18) and (19) relative to the axis of the drilling (4

[0016] The dose ejector (20) with a diameter slightly smaller than the bore (4) is moved by the free piston (21). The threaded rod sets the displacement height of the free piston with its locking nut (23) to the required dosing position. The mass of the dose can be determined by a precision balance.

[0017] The free piston (6) can be replaced by a conventional pneumatic micro-cylinder.

[0018] Its simplicity brings many advantages for the design of automatic machines.

[0019] The diameter will be chosen according to the force to be applied by the ball (15) to ensure the closure of the hole, subjected to the pressure necessary to move the product, when loading the next dose into the space (2). Automatic dosing of powders is very complex for certain powders and often requires a lot of adjustment work without absolutely guaranteeing repetitive results.

[0020] Powders are sensitive to many physicochemical factors, which requires a different approach for the automatic dosing of small quantities.

[0021] Experience dictates that the entire flow issue must be eliminated to ensure a stable result.

[0022] The movement of a powder in a tube in dense phase requires a pressure dependent on the diameter and length of the tube. The free piston (6) can transmit a pneumatic force of up to tens of bars on the product to be moved in the bore (2) and thus guarantees the presence of the dose before its ejection. The free piston (11) can replace the piston (6) by filling the bore (2) by suction for products not requiring a large force for moving the product and if necessary the piston (6) can fill the chamber (5) also by suction. The valve (9) is open for this operation.

[0023] The applications of the presented process are essentially intended for the multiple dosing of small quantities and require an industrial vision of manufacturing the dosers. Fig. 6 represents a device (21). intended for the dosing of a quantity of 1 mg

[0024] The filling zone (4) may, for example, have a diameter of 0.8 mm and a length of 1 mm. This quantity may be variable by adjusting the height of the dose ejector (20) 1. METHOD FOR CONTINUOUSLY MIXING POWDERS BASED ON THE INVENTION DESCRIBED

[0025] In the example Fig. 7, 2 sets of 4 dosers (22) and (23) according to Fig. 6 simultaneously dose 4 different products into 2 tubes (20) subjected to a vacuum intended to produce a continuous mixture. For this purpose, the proposed system can be adjusted to simultaneously dose 1 dose of 4 different products from the set (22), while the 4 doses from the set (22) are ejected into the mixture outlet tube (25).

[0026] This is how a discontinuous set becomes continuous.

[0027] Fig 7

[0028] During the dosing phase in the tube (20), the latter is subjected to a depression by the free piston which leads to densification of the 4 dosed powders and makes it possible, for example, to produce agglomerates of particles comprising all 4 different products of the example.

[0029] (Fig.8) shows the product tanks (26) of the 4 components that feed the dosers Fig (21). Dosage control can be carried out by a precision balance when the measurement stability is not affected by environmental conditions such as vibrations. The use of a laser detector, associated with each doser, is also possible in certain cases. (21 a).

[0030] Fig.8

[0031] For pasty products, this device can be used to introduce very small quantities to correct a situation. The field of highly viscous inks is one area of ​​application.

[0032] 2. PROCESS FOR MANUFACTURING PHARMACEUTICAL TABLETS BASED ON THE INVENTION DESCRIBED.

[0033] An important application of the invention is the manufacture of pharmaceutical tablets,

[0034] Compression is one of the most widely used processes in the pharmaceutical industry.

[0035] The Swiss consume several hundred million tablets per year.

[0036] This is a very complex technology that involves many sciences but still remains fairly empirical.

[0037] The FDA estimates that problems with solid-drug formulation cost billions of dollars annually. (Source 1)

[0038] The tablet is obtained by compressing a mixture of powders.

[0039] The mixture includes all the products, i.e. the active ingredient(s) and the excipients.

[0040] It must maintain the mixing proportions during manufacturing, which requires a perfect flow of the mass without modification of the mixture before compression. In industrial manufacturing, the individual dose is rarely controlled for its active substance content.

[0041] The mixture is statistically controlled by taking samples from the mixed mass, before compression.

[0042] The flowability of powders for their introduction into the compression space is the result of inter-particle interactions as well as with the environment.

[0043] The parameters influencing the flowability of powders are, above all, intrinsic, such as morphology, porosity, water content and others. Extrinsic parameters are subject to manufacturing and storage history as well as mechanical stresses and environmental parameters. For example, the influence of relative humidity can also play a role on interparticle adhesion forces.

[0044] Direct compression is in principle the simplest method for producing tablets since it eliminates the granulation step.

[0045] The manufacture of tablets requires the precise dosage of small quantities of active substance.

[0046] The principle proposed in (Fig.9) for the dosage of powders also allows the use of pastes, or even liquids, which is not possible with conventional processes.

[0047] CIP cleaning of pipes can be considered using this technique when changing products.

[0048] Mixing powders containing very low doses of certain components is very difficult, if not impossible, to maintain in its initial dosage due to the natural or mechanical mismixing of the components.

[0049] The mixing operation is almost always accompanied by a competitive mixing process called segregation. This process generally results in a non-homogeneous spatial distribution of the different powders.

[0050] Particle size plays a major role. It is critical for flow properties. Segregation is generally eliminated with particles below 10 mp. However, this fineness can block the mobility of the powder.

[0051] Relative humidity, electrostatic charges and van der Waals forces also play an important role in the flow process.

[0052] The stability of the mixture is for the galenic and therapeutic quality.

[0053] It is subject to statistical controls before the compression operation.

[0054] In general, the mixture samples are taken from the mass with a device allowing 30 g to be withdrawn for control.

[0055] To enable a quantitative analysis of the quality of the mixture, a statistical measure of heterogeneity is generally used. Work by the HES-SO has demonstrated large variations in values ​​compared to doses of 30 g (FDA standard) with doses of 1 g for a desired concentration of 2%.

[0056] (SOURCE: ELSEVIER Mixing effectiveness of a new pneumatic Batchmixer 2012.01 008

[0057] 5.

[0058] In all cases, the active substance content of the tablets is subject to statistical control, which is not carried out directly on the tablet, but on the mixture before compression.

[0059] The flow of the mixed mass into the compression machine brings potential demixing which can lead to uncertainties about the active substance content of the tablets.

[0060] Granulation simplifies the process by improving the flow properties of the mixture. It increases particle density and improves the homogeneity of the mixture by preventing the segregation of powders of different particle sizes. The size of the mixing loads obviously plays a major role, hence the current trend towards researching and developing continuous systems.

[0061] Flow properties are often improved by lubricants that limit the forces

[0062] The method shown in (F9 a) and (Fig 9-b) represents an example, based on the proposed invention, of an installation capable of dosing and compressing 64 pharmaceutical tablets in a time interval of approximately 4 sec and leading the machine to produce approximately 50,000 tablets per hour containing an active substance of 1 mg, the presence of which is controlled.

[0063] Fig.9. a

[0064] Fig. 9a. shows a schematic top view of the machine.

[0065] This is therefore an example of the possibilities offered by using the concept described in Fig.1.

[0066] The installation comprises a rotating disc (27) with 64 openings (21) into which the products, excipients and active substance (21) will be dosed.

[0067] These openings are closed at their base by the punches (32). The disc (27) is connected to the punch support (33) and disc (34).

[0068] The assembly (27), (33), ((34) is set in common rotation by a stepper motor, for example of 200 steps (35), described in (Fig. 9b), comprising a splined shaft to allow the vertical movement of the disc (34) The support (30) carries the assembly of punches (35) intended for compression. The lower punches (32) intended for closing and ejecting the tablets are carried by the disc (34).

[0069] Fig.9.b

[0070] In this example, the 64 dosers (21) are fixed on the structure (37), as are the free piston spaces of (Fig.1).

[0071] The feed of the dosing units with products to be dosed is carried out for each product by the tanks (7), Fig.1. which can be connected to a pumping system (38).

[0072] Compression is carried out by means of a hydraulic group (39), adapted to the compression force necessary to obtain the tablets (42)

[0073] Positions (28) and (29) of Fig.9a are shown in Figs. (10) and (11)

[0074] Fig. 10 shows the position of the disc 27 for dosing one or more products of the future tablet. The output of the dose can be controlled for example by the laser detector 21a of the corresponding device (21). Fig. 11 represents the tablets having received the hydraulic force of the cylinder (39), during the movement of the support (33) of the punches (35).

[0075] Fig. 12 shows the exit of the tablets from the disc 27 at the position which allows the tablets to then fall onto the channel due to the presence of the obstructor (29a) at the passage of (29), according to Fig. (9a)

[0076] The disc (34) is placed on fixed supports (40) having spheres (40a) to allow it to roll during rotation.

[0077] These are obviously examples of the process which is the subject of this filing, usable for many applications such as the dosing of powders for airbags, the correction of the shade of printing inks.

[0078] Generally speaking, this process allows small quantities of powder to be dosed without having to modify the structure of the product or add a component to facilitate flow in the dosing system.

Claims

Claims:

1. Device and method as described in this description 2. Method for continuous mixing of powders, based on claim 1 3. Methods of manufacturing pharmaceutical tablets, based on claim 1,

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